Transcript Enzyme Lab - Strive Studios

Enzyme Lab
Dr. Ippolito
BIO121 SUMMER II 2008
Materials
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Test Tubes
Sulfuric Acid
3% Hydrogen peroxide
Liver homogenate
pH 3 buffer
pH 7 buffer
pH 11 buffer*
Goals
• Understand and quantify enzyme activity
• Practice the Principles of the scientific
method
• Develop laboratory skills
• Develop inductive / deductive reasoning
skills
Revised Data Table
please copy this exactly
Tube #
Conditions
1
Positive
Control
2
+ Strong Acid
3
pH 3
4
pH 7
5
pH 11
6
Temp 45 C
7
Temp 4 C
8
Temp 100 C
9
0.1x Substrate
Rel. Activity
(cm of bubbles)
Rx Time
(s)
NOTES
Background
September 2004 Molecule of the Month
Background
• Catalase: more accurately, hydrogen
peroxidase, this enzyme catalyzes the
breakdown of hydrogen peroxide to water
and molecular oxygen.
• Because it was the first enzyme truly
characterized, it has a historical name that
simply means “catalyst” enzyme.
• Reaction: 2 H2O2  2H2O + O2 (gas)
About Catalase
• Catalases are some of the most efficient enzymes found
in cells. Each catalase molecule can decompose millions
of hydrogen peroxide molecules every second.
• The cow catalase shown here (PDB entry 8cat) and our
own catalases use an iron ion to assist in this speedy
reaction.
• The enzyme is composed of four identical subunits, each
with its own active site buried deep inside.
• The iron ion, shown in green, is gripped at the center of
a disk-shaped heme group.
• Catalases, since they must fight against reactive
molecules, are also unusually stable enzymes. Notice
how the four chains interweave, locking the entire
complex into the proper shape.
Why the liver?
• The liver detoxifies dangerous molecules.
• What is a ‘dangerous’ molecule?
– Some are dangerous because they have a lot
of free energy.
– The liver carefully extracts this energy, like
diffusing a bomb.
– How? It oxidizes! It removes the high-energy
electrons.
Why the liver?
• One of the side-products includes a lot of
Hydrogen Peroxide, which while dangerous, is
much less dangerous than the toxic molecules
the liver processed.
• The final step in diffusing this energy is to
convert hydrogen peroxide into harmless water
and oxygen.
• So the liver has tons and tons of catalase,
because it has tons and tons of H202 to deal
with.
Get into groups and grab your
gear!
Expectations
Next Thursday: Hand in a SINGLE packet that contains:
1. Title Page (title, names, Summer II 2008).
Remember to email me % for group members.
2. Answers to questions 1-13 on page 29 of your lab
manual
3. Written summary of the 4 experiments One
paragraph per experiment is sufficient. WRITE YOUR
HYPOTHESES HERE!
4. A brief discussion on your results. Any unexpected
results, experimental errors, or simply an overall
conclusion can be concluded.